Modern agriculture is concerned with the production of crops used primarily for human and animal food, but in so doing there is often the need (in some cases by law) to protect the environment. In crop production there is also the need to lower production costs, and especially reduce the use of expensive pesticides and fertilizers. It is often an important aim, which is not always ful fi lled to apply fertilizers and pesticides only when needed, but in order for this strategy to succeed, a better understanding of biotic stress and associated in fl uences from plant breeding achievements is required. Therefore the impact of biotic stress and injury to plants and plant yield is not only of economic importance to agriculture but is directly related to other biological and environmental questions. For example, biological and economic decision made over the control of biotic stress forms an important part of Integrated Pest Management (IPM). In this chapter, we deal with the latest results and conclusions of yield losses in plant pathology, entomology and weed science, and successful application of breeding approaches to limiting such yield reductions.

The element selenium (Se) is considered a finite and non-renewable resource on earth, and has been found to be an essential element in humans, animals, micro-organisms and some other eukaryotes; but as yet its essentiality to plants is in dispute. There is no doubt that adequate levels of selenium are important to animal and human health, and some selenium compounds have been found to be active against cancers. A limited number of plants growing on selenium rich soils can accumulate very high levels of selenium (i.e., hyperaccumulate selenium), and are classified as selenium tolerant, however, many more plants do not accumulate selenium to any great extent, and are selenium sensitive. Plants vary considerably in their physiological and biochemical response to selenium, and a revision of the physiological responses of plants to selenium is presented; especially growth, uptake, transport and interaction of selenium with other minerals.

The predominant proteins and enzymes in the sapwood and transition zones of Robinia pseudoacacia L. were identified and expressed by two methods: 2D SDS-PAGE (two-dimensional sodium dodecyl sulphate polyacrylamide gel electrophoresis) and electrospray io

Plant species composition in Ba Be National Park, Vietnam identified five plants that were rare and endangered and at serious risk of disappearing from the park. However, only Sinocalamus mucclure (string bamboo) and Markhamia stipulata had sufficient numbers to warrant molecular analysis. ISSR (Inter Simple Sequence Repeats) and RAPD-PCR (Random Amplified Polymorphic DNA-Polymerase Chain Reaction) were used to determine genetic differences between populations of Sinocalamus mucclure and Markhamia stipulata and whether genetic diversity was correlated to geographic distance. Disturbance in the area was evident, however, biogeography features usually associated with human disturbance was a minor contribution to species fragmentation. Analysis of similarity in biogeography and vegetation parameters demonstrated that similarity between the sites was between 65 and 85% and introduced plant species to the park was low. Trees dominated the canopy and species richness varied between the sites. Multi-Dimensional Scaling (MDS) of molecular data showed significant differences in populations of both plants and that substantial genetic variation between individuals of both species were present. ISSR revealed slightly less genetic diversity in both species (70-71% polymorphism) than RAPD-PCR (65-71% polymorphism). In conclusion, ISSR appeared to be more discriminatory than RAPD-PCR but both were versatile, sensitive and cost effective methods for use in genetic diversity and conservation genetics.